Some cells are uncontrolled in the sense that a PLMN (public land mobile network) operator does not control the location and/or operation of the cell. Other cells are controlled in the sense that the operator does control the both the location and operation of the cells. Examples of uncontrolled cells include, for example, CSG (closed subscriber group) cells, cells controlled by home enode b's and home node b's. These cells are also sometimes referred to as being “uncoordinated” in the sense that they are not subject to normal radio/cell planning.
It is generally understood that there are many methods of performing a handover for controlled cells. Inbound handover in this context refers to a cell change from a target cell's perspective where resources (for example timeslots, frequency channels, scrambling codes, etc.) for transmission and/or reception in the cell are allocated to a mobile station in advance of the mobile station performing a cell change to that cell, particularly in response to a request from the controller of the device's serving cell.
While the uncontrolled cells may be configured to use spectrum that is owned by the operator, the network operator does not have the same control over uncontrolled cells as for controlled cells. Typically, the network operator does not own the support structure (towers etc.), does not own or control the backhaul connection (e.g. Digital Subscriber Line (DSL) connections), does not know or control when a given uncontrolled cell is going to be switched on, and may not know or control the locations of uncontrolled cells. The operator will typically still have control of various parameters such as operating frequency, transmit power, etc. if the operator owns the spectrum license.
In order to perform a handover to a target cell, controlled or uncontrolled, a MS (mobile station) typically needs to provide identifying information relating to the target cell to the current serving cell so that it can initiate a handover process. In particular, the current serving cell needs to be able to communicate with (possibly via a core network) the cell controller for the target cell. However, the current serving cell may not be aware of how to reach the cell controller for the target cell, particularly if the target cell is an uncontrolled cell, unless provided with explicit identification information for the cell (such as a cell global identity). This makes handover to such cells difficult. In contrast, for a controlled target cell, it may be sufficient for the mobile station to provide the current serving cell with information about the target cell. This does not require or cause the acquisition of any broadcast information from the target controlled cell for the serving cell to be able to reach the cell controller for the target controlled cell, since the serving cell or some part of the network may be able to map other identifying features of the cell (such as operating frequency, scrambling code etc.) to the identity of the target cell or its controller.